Ok I am very new to machining, i bought a atlas 618 lathe and have been messing around making some small parts, anyway my auto feed will not stay engaged, not sure if there is something that is supposed to keep it engaged or just the gear mesh keeps it engaged. I can hold down on the banjo? Not sure if that is the correct name or not and it will work, thumb gets tired though, any info would be appreciated, if there is a better way to explain let me know. Thanks
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618 auto feed question
- Thread starter Alanv
- Start date
Im definatly not the one to give advise, as Im new at this too. But my 101 has a problem with the auto feed as in certian places it wont stay feeding. I had posted pics of my half nut and the guys here said it looked worn, so I got a new one today. Hopfully this will fix my problem, and give you something to look at on yours.
- Joined
- Dec 25, 2011
- Messages
- 10,552
Alanv,
There is a detent spring and ball that operate on the M6-38 Cam. Download the 618 manual and look on page 11. Possibly someone had it apart and lost one or both parts.
Aside from those parts being missing, any time that you have trouble engaging the half nuts or in them staying engaged, besides wear on the half nuts, the other thing to check for is the vertical location of the lead screw. If the lead screw lifts or drops when you engage the half nuts, the bearings at one end or the other need adjustment. To adjust, move the carriage to the tailstock end of the bed. Loosen the two cap screws holding the bearing. Engage the half nuts (you may have to rock the carriage back or forth to do this). Tighten the cap screws. Move the carriage to the headstock end of the bed. Remove the Change Gear Bracket Assembly. Loosen the two cap screws holding the bearing and engage the half nuts. Tighten the cap screws. Reinstall the Change Gear Bracket Assembly.
The "Banjo" is another name for the cast Change Gear Bracket on the left end of the headstock that holds all but one of the Change Gears. The part that you have been holding down is called the Split Nut Lever (or Half Nut Lever).
Robert D.
There is a detent spring and ball that operate on the M6-38 Cam. Download the 618 manual and look on page 11. Possibly someone had it apart and lost one or both parts.
Aside from those parts being missing, any time that you have trouble engaging the half nuts or in them staying engaged, besides wear on the half nuts, the other thing to check for is the vertical location of the lead screw. If the lead screw lifts or drops when you engage the half nuts, the bearings at one end or the other need adjustment. To adjust, move the carriage to the tailstock end of the bed. Loosen the two cap screws holding the bearing. Engage the half nuts (you may have to rock the carriage back or forth to do this). Tighten the cap screws. Move the carriage to the headstock end of the bed. Remove the Change Gear Bracket Assembly. Loosen the two cap screws holding the bearing and engage the half nuts. Tighten the cap screws. Reinstall the Change Gear Bracket Assembly.
The "Banjo" is another name for the cast Change Gear Bracket on the left end of the headstock that holds all but one of the Change Gears. The part that you have been holding down is called the Split Nut Lever (or Half Nut Lever).
Robert D.
Thanks to both of you, i will to find and down load that manual, and check out that detent ball and spring, apparently my lead screw does need to be adjusted it it bows up when i engage the half nuts. I am actually pushing down on the banjo to keep the gears engaged, the half nuts stay engaged by themselves my problem is at the end where the gears are, anyway i will download the manual and start with your recommendations and go from there, and report back my findings, thanks, Alan
Ok i took the banjo aka as the M6-25 bracket apart to see how it all work and cleaned all of the parts, from looking at it i am guessing that the clamp mechanism part of the M6-25 bracket is what holds the gears engaged? I had that snug but not real tight. Am i correct that this is what keeps the gears engaged? If so i will try to tighten it and see if that works or maybe the M6-27 is worn where the banjo sets, and here are some pics of the gearing
Last edited:
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- Dec 25, 2011
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Yes. The pinch bolt locks the M6-25 Bracket relative to the nose of the M6-27 left leadscrew bearing. I misunderstood your first post, probably because I was half asleep and there have been several threads lately (here and elsewhere) that reported problems with the half nuts not staying closed.
There is a slot sawn from the large hole in the bracket out the right end. The slot allows the pinch bolt to clamp the hole around the nose of the bearing. In your first photo showing the right end of the bracket I can't see the slot. Is it completely closed? With the screw gear removed, check it with a thin feeler gauge (~.005"-.010"). You should be able to slide the gauge all the way from the right end of the slot to the bearing.
Robert D.
There is a slot sawn from the large hole in the bracket out the right end. The slot allows the pinch bolt to clamp the hole around the nose of the bearing. In your first photo showing the right end of the bracket I can't see the slot. Is it completely closed? With the screw gear removed, check it with a thin feeler gauge (~.005"-.010"). You should be able to slide the gauge all the way from the right end of the slot to the bearing.
Robert D.
It was probably my description that confused you, we are on the same page now so, with the pinch bolt loose i have .015 in the slot all the way from one end to the other and when i tighten the bolt i can not fit a feeler guage in there at all, i just tried it with the pinch bolt tight and it worked great, i will keep an eye out for a replacement M6-27 because i think the one i have is worn. Thanks for all your help, i am sure i will have other questions as i keep playing with this thing
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- Dec 25, 2011
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OK. If fully tightened it doesn't slip, I would take a "if it ain't broke, don't fix it" stance. However, if it starts slipping again before you can source a replacement left leadscrew bearing, you can try re-sawing the gap with up to about an 0.022" thick hacksaw or bandsaw blade. I don't think that I would go any farther.
Robert D.
Robert D.